// Copyright 2014 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "ui/views/view_targeter_delegate.h"

#include <limits.h>

#include "ui/gfx/geometry/rect_conversions.h"
#include "ui/views/rect_based_targeting_utils.h"
#include "ui/views/view.h"

namespace {

// The minimum percentage of a view's area that needs to be covered by a rect
// representing a touch region in order for that view to be considered by the
// rect-based targeting algorithm.
static const float kRectTargetOverlap = 0.6f;

} // namespace

namespace views {

// TODO(tdanderson): Move the contents of rect_based_targeting_utils.(h|cc)
//                   into here.

bool ViewTargeterDelegate::DoesIntersectRect(const View* target,
    const gfx::Rect& rect) const
{
    return target->GetLocalBounds().Intersects(rect);
}

View* ViewTargeterDelegate::TargetForRect(View* root, const gfx::Rect& rect)
{
    // |rect_view| represents the current best candidate to return
    // if rect-based targeting (i.e., fuzzing) is used.
    // |rect_view_distance| is used to keep track of the distance
    // between the center point of |rect_view| and the center
    // point of |rect|.
    View* rect_view = NULL;
    int rect_view_distance = INT_MAX;

    // |point_view| represents the view that would have been returned
    // from this function call if point-based targeting were used.
    View* point_view = NULL;

    for (int i = root->child_count() - 1; i >= 0; --i) {
        View* child = root->child_at(i);

        if (!child->CanProcessEventsWithinSubtree())
            continue;

        // Ignore any children which are invisible or do not intersect |rect|.
        if (!child->visible())
            continue;
        gfx::RectF rect_in_child_coords_f(rect);
        View::ConvertRectToTarget(root, child, &rect_in_child_coords_f);
        gfx::Rect rect_in_child_coords = gfx::ToEnclosingRect(
            rect_in_child_coords_f);
        if (!child->HitTestRect(rect_in_child_coords))
            continue;

        View* cur_view = child->GetEventHandlerForRect(rect_in_child_coords);

        if (views::UsePointBasedTargeting(rect))
            return cur_view;

        gfx::RectF cur_view_bounds_f(cur_view->GetLocalBounds());
        View::ConvertRectToTarget(cur_view, root, &cur_view_bounds_f);
        gfx::Rect cur_view_bounds = gfx::ToEnclosingRect(
            cur_view_bounds_f);
        if (views::PercentCoveredBy(cur_view_bounds, rect) >= kRectTargetOverlap) {
            // |cur_view| is a suitable candidate for rect-based targeting.
            // Check to see if it is the closest suitable candidate so far.
            gfx::Point touch_center(rect.CenterPoint());
            int cur_dist = views::DistanceSquaredFromCenterToPoint(touch_center,
                cur_view_bounds);
            if (!rect_view || cur_dist < rect_view_distance) {
                rect_view = cur_view;
                rect_view_distance = cur_dist;
            }
        } else if (!rect_view && !point_view) {
            // Rect-based targeting has not yielded any candidates so far. Check
            // if point-based targeting would have selected |cur_view|.
            gfx::Point point_in_child_coords(rect_in_child_coords.CenterPoint());
            if (child->HitTestPoint(point_in_child_coords))
                point_view = child->GetEventHandlerForPoint(point_in_child_coords);
        }
    }

    if (views::UsePointBasedTargeting(rect) || (!rect_view && !point_view))
        return root;

    // If |root| is a suitable candidate for rect-based targeting, check to
    // see if it is closer than the current best suitable candidate so far.
    gfx::Rect local_bounds(root->GetLocalBounds());
    if (views::PercentCoveredBy(local_bounds, rect) >= kRectTargetOverlap) {
        gfx::Point touch_center(rect.CenterPoint());
        int cur_dist = views::DistanceSquaredFromCenterToPoint(touch_center,
            local_bounds);
        if (!rect_view || cur_dist < rect_view_distance)
            rect_view = root;
    }

    return rect_view ? rect_view : point_view;
}

} // namespace views
